Fire control includes the direction, range, grouping and speed of fire; the selection of the target, of the guns to be used, when they are to be used; and control of the character of the ammunition employed. The chief fire-control officer of a ship is in constant communication with the captain; the chief fire-control officer of a group of guns or batteries on shore keeps in dose touch with the commanding officer of the group, as changes in target or character of fire are of frequent occurrence — shifts from ordinary shell to gas shell and then to shrapnel being sometimes made in a single minute. Each subdivision of a group of guns, if likely to be assigned a separate target or different ammu nition, or if the guns of the subdivision are of a different calibre or type, or at some distance from the rest of the group, must have its own fire-control officer, who gets general instruc tions from the chief fire control. Small-arm fire from muskets or machine guns is usually controlled by the commanding officer of the infantry unit to which they belong or near which they are located. The present character and arrangement of the battery of recent battle ships is based upon the fundamental principle of, strategy which requires the greatest con centration of gun-power in the least practicable space, but the reform was largely brought about by tactical difficulties connected with the fire control of guns of several calibres. These difficulties are too complex for full description here but were connected with the fact that guns of different calibres have different maximum ranges, different danger spaces at practically all ranges, and must often be directed at different targets. This involved a serious complication in fire control. The strategical arguments for the all-big-gun battleship backed by tactical ones forced the adoption of the principle. Since the maximum weight of fire can only be obtained on the broadside, the fullest development of broadside fire led to placing all turrets on the central fore-and-aft line, while good bow-fire and stern-fire were obtained by raising two turrets so they could fire over others. The difficulties of fire control were thus reduced to their lowest terms while the gun-power of the ship was enormously increased. Another stra tegic gain was the augmented gun-power of the line of battle of the fleet for each thou sand yards of its length, in ships of recent type, the gun-power per thousand yards of the line of battle is 500 per cent greater than for ships of the Connecticut class and is accompanied with an increase of speed of more than four knots, much greater range of guns, superior accuracy at all ranges beyond a few thousand yards and enormously greater destructive effect of the projectiles.
In land operations, artillery fire is designed to: (a) check the enemy's advance by (1) in terposing a barrage or curtain of fire between his front and his objective or by (2) fire di rected at his advancing troops; (b) prevent the advancing of the enemy's reinforcements by interposing a barrage between his fighting line and his reserves or supporting troops; (c) de stroy the enemy's stores or interrupt his sup plies; (d) destroy his field works, trenches and gun-emplacements or render them untenable or useless; (e) clear the ground of the enemy's obstructions in preparation for advance or assault; (f) to lower the morale or resisting power of the enemy by very heavy bombard ment, use of gas, etc.; (g) to deceive the enemy as to the true objective but incidentally to inflict all possible damage.
While field guns of about 3-inch calibre have the widest range of usefulness in attack and defense, large guns (up to 12-inch calibre) of great power and long range are often of great service, and heavy howitzers (up to 20-inch, but especially of 8- to 12-inch) are indispen sable. Concealment of the positions of heavy guns is more important than any form of pro tection and where practicable they are f ree quently moved, some being placed on railway cars. Concealment from airplane observation is sought by covering with brush or light un noticeable screens, or by painting the gun and mount in a way to render its identification difficult.
Trench mortars are very light pieces de signed to throw heavy charges (25 to 200 pounds) of high explosive a distance of a few hundred feet and are very useful when the enemy's trenches and other works arc near your own. Most trench mortars are of three- or four-inch calibre but a few are much larger. The propulsive force is compressed air or a small charge of powder. In place of these mortars, simple catapults, with long arms oper ated by compressing some sort of spring, have been used with considerable success at very short distances. To obtain high efficiency of operation, the gun-layers, gun-pointers, sight setters, trainers and all other men attached to a gun or battery must be highly trained. Those who sight the guns must have a preliminary training of months to get the best results. And only a few men have the keenpess of vision, steadiness of nerve and quickness of decision, which are required for gun-pointers of the first class. The character of the work required in the army and the navy is very different, that of naval gun-layers being much more difficult, because the gun itself is on a moving platform which rolls and pitches. This makes it neces sary to have two men, one (the trainer) who trains the piece and keeps it in the vertical plane of the target and one (the pointer) who elevates the gun and fires. A third man (the sight-setter) keeps the angle of elevation (be tween the line of sight and the axis of the bore) adjusted in accordance with instructions. Gun-pointers are trained by a progressive sys tem which begins with aiming a gun at a very small point. The next step is the use of an instrument which records the point aimed at. This is followed by sub-calibre practice in which a piece of small calibre is clamped to the large gun. The sights of the large gun are used but it is the small one which is fired. Sub-calibre practice lends itself to many variations, the methods in use in different navies and armies being alike only in principle. Full-calibre tar get practice follows sub-calibre work and battle practice (in which the conditions of battle are simulated) complete the training. Hardly less important than the foregoing is the training of the ammunition supply details; in modern field fighting, upon a thorough organization and efficiency of the supply train depends the win ning or losing of the battle. See articles on GUNS; BALLISTICS; PROJECTILES, etc.
Consult (Text-book on Naval Ordnance' (Annapolis 1914) ; Bethell's Guns and Gunnery' (Woolwich 1910) ; 'Modern Artillery in the Field' (New York, 1911) ; Lissak's (Ordnance and Gunnery> (New York 1907) ; Proceedings of the United States Naval Institute' (Annapolis, Md.) ; Journal of the United States Artillery (Ft. Monroe, Va.), and Field Artillery Journal (Washington, D. C.).